CN115044179A

CN115044179A - Plasticized polylactic acid composite material and preparation method thereof

Info

Publication number: CN115044179A
Application number: CN202210677831.7A
Authority: CN
Inventors: 郑强; 黄绍文; 王彦文; 李娟�; 高成涛; 罗珊珊
Original assignee: Guizhou Material Industrial Technology Research Institute
Current assignee: Guizhou Material Industrial Technology Research Institute
Priority date: 2022-06-15
Filing date: 2022-06-15
Publication date: 2022-09-13

Abstract

The invention discloses a plasticized polylactic acid composite material and a preparation method thereof, wherein the plasticized polylactic acid composite material comprises polylactic acid, a plasticizer and a chain extender; the plasticizer has a polyol backbone and an oligomeric lactic acid segment grafted to one or more hydroxyl groups of the polyol. The plasticizer provided by the invention contains polylactic acid low molecular chain segments which are similar to polylactic acid molecular structures, so that the plasticizer has good compatibility with polylactic acid, is difficult to migrate out, and can not cause serious reduction of product strength; the film blowing polylactic acid of the invention is modified, has low processing temperature, high melt strength and good film blowing processability, and can realize the production of polylactic acid film products and bag products.

Description

Plasticized polylactic acid composite material and preparation method thereof

Technical Field

The invention belongs to the technical field of organic compound synthesis, and particularly relates to a plasticized polylactic acid composite material and a preparation method thereof.

Background

Traditional non-degradable plastics based on polyethylene, polystyrene and polypropylene are extremely harmful to the environment, and therefore biodegradable plastics are rapidly developed. The polylactic acid (PLA) has good biocompatibility and degradability, high strength and good transparency, so that the PLA has great application potential in the packaging industry and the pharmaceutical industry, but the PLA also has the problems of poor toughness, high processing temperature, low melt strength and difficulty in film blowing forming processing, thereby causing great limitation on the application of the PLA.

The plasticizer is the most used of various plastic additives, and the additive with the highest proportion is added into the plastic, and after the plasticizer is added, the glass transition temperature of polymer materials such as plastic, resin and the like is reduced, so that the plasticity and the processability are improved.

At present, most of common plasticizers for PLA are citric acid esters, fatty acid esters and polyethylene glycol, and the following problems exist: 1. the low boiling point leads to volatilization during processing; 2. the tensile strength of the product is seriously reduced due to large addition amount; 3. poor compatibility results in easy migration and precipitation on the surface. In addition, the addition of the conventional plasticizer for PLA can reduce the melt strength of PLA during processing, and the film blowing processing cannot be realized.

Disclosure of Invention

This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.

The present invention has been made keeping in mind the above and/or other problems occurring in the prior art.

One of the purposes of the invention is to provide a plasticized polylactic acid composite material which is modified, has low processing temperature, high melt strength and good film blowing processability and can realize the production of polylactic acid film products and bag products.

In order to solve the technical problems, the invention provides the following technical scheme: a plasticized polylactic acid composite material comprises polylactic acid, a plasticizer and a chain extender; the plasticizer comprises a polyol main chain and an oligomeric lactic acid chain segment which is grafted on one or more hydroxyl groups of the polyol and is shown in the formula I;

wherein n is a positive integer of 3-10.

As a preferable embodiment of the plasticized polylactic acid composite material of the present invention, wherein: the plasticizer is present in an amount of 5 to 20% by mass, and the chain extender is present in an amount of 0.1 to 0.8% by mass.

As a preferable embodiment of the plasticized polylactic acid composite material of the present invention, wherein: the chain extender comprises one or more of 4, 4' -dicyclohexylmethane isocyanate, isophorone diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, lysine diisocyanate, diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, Joncryl ADR 4300, Joncryl ADR4370, Joncryl ADR 4370S, Joncryl ADR 4380, Joncryl ADR 4385, Joncryl ADR 4468, KL-E4300, KL-E4370, KL-E43 4370B and TN 4300.

It is another object of the present invention to provide a method for preparing the plasticized polylactic acid composite as described above, comprising, providing a plasticizer; and (3) melting and blending the polylactic acid, the plasticizer and the chain extender, and extruding and granulating.

As a preferable embodiment of the method for preparing the plasticized polylactic acid composite material of the present invention, wherein: and carrying out melt blending at the processing temperature of 50-190 ℃.

As a preferable embodiment of the method for preparing the plasticized polylactic acid composite material of the present invention, wherein: the plasticizer is provided, and polyhydric alcohol and lactide are heated to react under the action of an organic tin catalyst.

As a preferable embodiment of the method for preparing the plasticized polylactic acid composite material of the present invention, wherein: the molar ratio of the lactide to the polyol is 20-200: 1.

as a preferable embodiment of the method for preparing the plasticized polylactic acid composite material of the present invention, wherein: the organic tin catalyst comprises dibutyltin oxide, dibutyltin dibutyrate, dimethyltin dibutyrate, dioctyltin dibutyrate, dibutyltin diacetate, dimethyltin diacetate, dioctyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dioctyltin dilaurate, dimethyltin dioleate, dioctyltin dioleate, isooctyldimethyltin dithioglycolate, dibutyltin dineodecanoate, dimethyltin dineodecanoate, dioctyltin dineodecanoate, dibutyltin diacetate, dimethyltin diacetate, dioctyltin diacetate, dibutyltin bisacetylacetonate, dibutyltin bisdodecylthioalkylate, dimethyltin oxide, dibutyltin dilaurylthio, dimethyltin oxide, tin oxide, zinc, One or more of dioctyltin oxide, stannous octoate, dibutyltin maleate, dimethyltin maleate, dioctyltin maleate, monobutyltin oxide and stannous oxalate.

As a preferable embodiment of the method for preparing the plasticized polylactic acid composite material of the present invention, wherein: the addition amount of the organic tin catalyst is 0.1-1% of the molar amount of the lactide.

As a preferable embodiment of the method for preparing the plasticized polylactic acid composite material of the present invention, wherein: the heating reaction is carried out at the reaction temperature of 130-160 ℃ for 4-6 h.

Compared with the prior art, the invention has the following beneficial effects:

the plasticizer contains polylactic acid low molecular chain segment, and has a similar molecular structure with polylactic acid, so that the plasticizer has good compatibility with polylactic acid, is difficult to migrate, and can not cause serious reduction of product strength. The plasticizer has high molecular weight, so the plasticizer is difficult to volatilize, has good heat resistance, is solid at normal temperature and is easy to use by hot processing. The film blowing grade polylactic acid is modified, has low processing temperature, high melt strength and good film blowing processing performance, and can realize the production of polylactic acid film products and bag products.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein:

FIG. 1 is a mass spectrum of the product of example 1 of the present invention;

FIG. 2 is a mass spectrum of the product of example 2 of the present invention;

FIG. 3 is a mass spectrum of the product of example 3 of the present invention;

FIG. 4 is a mass spectrum of the product of example 4 of the present invention;

FIG. 5 is a mass spectrum of the product of example 5 of the present invention;

FIG. 6 is an infrared comparison of the products of examples 1-5 of the present invention with polylactic acid;

FIG. 7 is a comparative thermogravimetric analysis chart of the products of examples 1-5 of the present invention and polylactic acid.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

The raw materials used in the examples were all purchased commercially unless otherwise specified.

Example 1

1.82g (0.01mol) of sorbitol, 28.8g (0.2mol) of lactide and 0.063g (0.1mmol, 0.05 mol) of dibutyltin dilaurate are added into a single-neck flask, fully dried, and subjected to oxygen removal and nitrogen replacement, then fully stirred, heated to 140 ℃ under the protection of nitrogen, reacted for 4 hours, cooled to room temperature after the reaction is finished, ground, soaked in ethanol and ultrasonically cleaned for 3 times, and vacuum-dried at 80 ℃ to obtain 27.86g of a white solid product with the yield of 91%.

The reaction equation is as follows:

the mass spectrum of the product of example 1 is shown in FIG. 1. The average molecular weight of the product of example 1 was about 1000 g/mol.

Example 2

1.52g (0.01mol) of xylitol, 28.8g (0.2mol) of lactide and 0.063g (0.1mmol, 0.05 mol) of dibutyltin dilaurate are added into a single-neck flask, fully dried, and subjected to oxygen removal and nitrogen replacement, fully stirred, heated to 140 ℃ under the protection of nitrogen, reacted for 4 hours, cooled to room temperature after the reaction is finished, ground, soaked in ethanol and ultrasonically cleaned for 3 times, and vacuum-dried at 80 ℃ to obtain 28.20g of a white solid product with the yield of 93%.

The reaction equation is as follows:

the mass spectrum of the product of example 2 is shown in FIG. 2. The average molecular weight of the product of example 2 was about 1400 g/mol.

Example 3

1.36g (0.01mol) of pentaerythritol, 28.8g (0.2mol) of lactide and 0.063g (0.1mmol, 0.05 mol) of dibutyltin dilaurate were added to a single-neck flask, and after fully drying and replacing nitrogen by oxygen, the mixture was kept fully stirred, heated to 140 ℃ under the protection of nitrogen, reacted for 4 hours, and after the reaction was finished, cooled to room temperature, the product was ground, soaked in ethanol and ultrasonically cleaned for 3 times, and vacuum-dried at 80 ℃ to obtain 26.84g of a white solid product with a yield of 89%.

The reaction equation is as follows:

the mass spectrum of the product of example 3 is shown in FIG. 3. The average molecular weight of the product of example 3 was about 1100 g/mol.

Example 4

1.34g (0.01mol) of trimethylolpropane, 28.8g (0.2mol) of lactide and 0.063g (0.1mmol, 0.05 mol) of dibutyltin dilaurate are added into a single-neck flask, fully dried, oxygen is removed, nitrogen is replaced, then full stirring is kept, the mixture is heated to 140 ℃ under the protection of nitrogen, reaction is carried out for 4 hours, after the reaction is finished, the mixture is cooled to room temperature, the product is soaked in ethanol and ultrasonically cleaned for 3 times after being ground, and vacuum drying is carried out at 80 ℃ to obtain 24.41g of white solid product with the yield of 81%.

The reaction equation is as follows:

the mass spectrum of the product of example 4 is shown in FIG. 4. The average molecular weight of the product of example 4 was about 1300 g/mol.

Example 5

In a single-neck flask, 1.06g (0.01mol) of diethylene glycol, 28.8g (0.2mol) of lactide, and 0.063g (0.1mmol, 0.05%) of dibutyltin dilaurate were added, followed by sufficient drying and replacement of nitrogen with oxygen, followed by sufficient stirring, heating to 140 ℃ under nitrogen protection, reacting for 4 hours, after completion of the reaction, cooling to room temperature, grinding the product, soaking in ethanol, ultrasonic cleaning for 3 times, and vacuum drying at 80 ℃ to obtain 25.08g of a white solid product with a yield of 84%.

The reaction equation is as follows:

the mass spectrum of the product of example 5 is shown in FIG. 5. The average molecular weight of the product of example 5 was about 2000 g/mol.

FIG. 6 shows the IR contrast of polylactic acid and the products of examples 1 to 5.

FIG. 6 shows that the products of examples 1-5 are very similar to the IR chart of polylactic acid, which indicates that the products of examples 1-5 have polylactic acid segments and are very compatible with polylactic acid.

FIG. 7 is a comparison graph of thermogravimetric analysis of the products of examples 1-5 and polylactic acid, and the test shows that the product of example 1 has 95% mass remaining at 165 ℃, the product of example 2 has 95% mass remaining at 187 ℃, the product of example 3 has 95% mass remaining at 195 ℃, the product of example 4 has 98% mass remaining at 223 ℃, the product of example 5 has 95% mass remaining at 228 ℃, and the products of examples 4 and 5 have higher stability. The result shows that in the series of plasticizers, the product with less hydroxyl groups has higher thermal stability, wider processing window and application range.

Example 6

Preparing blown film grade polylactic acid:

melt blending, extrusion and granulation were carried out on 200 g of each of the products of examples 1 to 5, 800 g of polylactic acid (obtained from NatureWorks, USA) and 5 g of Joncryl ADR4370 (obtained from Pasfu, Germany) by means of a twin-screw extruder to obtain blown film grade polylactic acids A to E.

1000g of polylactic acid and 5 g of Joncryl ADR4370 are melted, blended, extruded and granulated by a double-screw extruder to obtain blown film grade polylactic acid F.

And respectively blowing the obtained film blowing grade polylactic acids A to F in a film blowing machine to respectively obtain films A to F.

The temperatures of the twin-screw extruder were 50 ℃, 170 ℃, 175 ℃, 180 ℃,185 ℃. The blow-up ratio was 1: 1.4. The processing temperatures of the film blowing machine are respectively 100 ℃, 180 ℃,185 ℃, 190 ℃, 195 ℃ and 200 ℃.

The obtained films A to F are subjected to mechanical property test by adopting a test method GB/T1040.3-2006, and the test results are shown in Table 1.

TABLE 1

	Tensile Strength (MPa)	Elongation at Break (%)
			Film A	33.20	62.4
Film B	38.64	162.8
			Film C	29.55	216.6
Film D	59.53	55.4
			Film E	65.79	38.1
Film F	77.65	3.4

As shown by comparison, the film F without the plasticizer had a very low elongation at break and was very brittle. In the film A, the plasticizer of example 1 is decomposed at a low temperature, so that the plasticizer is decomposed more strongly during processing, the tensile strength is seriously reduced, and the elongation at break is not greatly improved. The film D and the film E have a reduced plasticizing effect due to an excessively long polylactic acid segment in the plasticizer. In general, the film B and the film C are preferable.

Example 7

Preparing blown film grade polylactic acid:

200 g of the product of example 3, 800 g of polylactic acid (purchased from NatureWorks company, USA) and chain extenders with different types and addition amounts are taken, and melt blending extrusion granulation is carried out by a double-screw extruder to obtain blown film grade polylactic acids A1-A8, wherein the types and addition amounts of the chain extenders are specifically shown in Table 2.

Respectively blowing the obtained film blowing grade polylactic acid A1-A8 in a film blowing machine to respectively obtain films A1-A8.

The obtained films A1-A8 are subjected to mechanical property tests, the test method adopts GB/T1040.3-2006, and the test results are shown in Table 2.

TABLE 2

As can be seen from table 2, the film a7 without the addition of the chain extender had a higher tensile strength but a lower elongation at break; the tensile strength of the film added with the chain extender is obviously reduced, and the elongation at break is obviously improved; under the same reaction conditions, 4' -dicyclohexyl methane isocyanate and TN4300 are used as chain extenders, so that the tensile strength and the elongation at break of the film A2 and the film A4 are lower; and the film A1 and the film A3 can obtain better mechanical properties by adopting Joncryl ADR4370 and KL-E4370 as chain extenders.

When Joncryl ADR4370 is used as the chain extender, the film A1 is more preferable because the tensile strength gradually increases and the elongation at break gradually decreases with the increase in the amount of Joncryl ADR4370 used.

Example 8

Example 8 is essentially the same as example 1, except that the catalyst type is different, as shown in table 3 below:

TABLE 3

Catalyst and process for preparing same	Dosage of	Yield of
			Dibutyl tin dibutyrate	0.05％	87％
Dibutyl tin dilaurate	0.05％	91％
			Stannous octoate	0.05％	89％
Stannous oxalate	0.05％	85％
			Dibutyltin isooctyl dithioacetate	0.05％	87％
Dioctyltin diacetate	0.05％	88％
			Diacetone dibutyl tin	0.05％	80％
Monobutyl tin oxide	0.05％	75％
			Dibutyl tin dilaurate	0.1	92％
Dibutyl tin dilaurate	0	0
			Dibutyl tin dilaurate	0.3	95％
Dibutyl tin dilaurate	0.5	96％

As can be seen from Table 3, the yield was up to 91% under the same reaction conditions with dibutyltin dilaurate as catalyst.

Although the yield is further improved by increasing the addition amount of dibutyltin dilaurate, the molecular weight of the product is reduced, and particularly when the addition amount reaches 0.5%, the average molecular weight of the product is only 600g/mol, the molecular weight is low, thermal decomposition is easy, and the subsequent use is influenced.

Example 9

Example 9 is essentially the same as example 1, except that the reaction temperature and time are different, as shown in table 4 below:

TABLE 4

Temperature of	Time	Yield of
			130℃	4h	85％
130℃	6h	86％
			130℃	8h	86％
140℃	4h	91％
			150℃	4h	91％
160℃	4h	92％

As can be seen from Table 4, the reaction yield was low at 130 ℃ and the reaction time was prolonged, the reaction yield was not greatly improved, the reaction temperature was increased to 150 ℃ and 160 ℃ and the reaction yield was substantially unchanged, and 140 ℃ was a preferred reaction temperature from the viewpoint of fuel power cost.

The plasticizer provided by the invention has a molecular structure similar to that of polylactic acid, so that the plasticizer has good compatibility with the polylactic acid, is difficult to migrate out, and cannot cause serious reduction of product strength. The plasticizer has high molecular weight, so the plasticizer is difficult to volatilize, has good heat resistance, is solid at normal temperature and is easy to use by hot processing. The film blowing grade polylactic acid is modified, has low processing temperature, high melt strength and good film blowing processing performance, and can realize the production of polylactic acid film products and bag products.

It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims

1. A plasticized polylactic acid composite characterized by: comprises polylactic acid, plasticizer and chain extender; the plasticizer comprises a polyol main chain and an oligomeric lactic acid chain segment which is grafted on one or more hydroxyl groups of the polyol and is shown in the formula I;

wherein n is a positive integer of 3-10.

2. A plasticized polylactic acid composite according to claim 1, wherein: the plasticizer is present in an amount of 5 to 20% by mass fraction, and the chain extender is present in an amount of 0.1 to 0.8% by mass fraction.

3. A plasticized polylactic acid composite according to claim 1, wherein: the chain extender comprises one or more of 4, 4' -dicyclohexylmethane isocyanate, isophorone diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, lysine diisocyanate, diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, Joncryl ADR 4300, Joncryl ADR4370, Joncryl ADR 4370S, Joncryl ADR 4380, Joncryl ADR 4385, Joncryl ADR 4468, KL-E4300, KL-E4370, KL-E43 4370B and TN 4300.

4. The method of producing a plasticized polylactic acid composite according to any one of claims 1 to 3, wherein: comprises the steps of (a) preparing a mixture of a plurality of raw materials,

providing a plasticizer;

and (3) melting and blending the polylactic acid, the plasticizer and the chain extender, and extruding and granulating.

5. The method of preparing a plasticized polylactic acid composite according to claim 4, wherein: and carrying out melt blending at the processing temperature of 50-190 ℃.

6. The method of preparing a plasticized polylactic acid composite according to claim 4 or 5, wherein: the plasticizer is provided, and polyhydric alcohol and lactide are heated to react under the action of an organic tin catalyst.

7. The method of preparing a plasticized polylactic acid composite according to claim 6, wherein: the organic tin catalyst comprises dibutyltin oxide, dibutyltin dibutyrate, dimethyltin dibutyrate, dioctyltin dibutyrate, dibutyltin diacetate, dimethyltin diacetate, dioctyltin diacetate, dibutyltin dilaurate, dimethyltin dilaurate, dioctyltin dilaurate, dimethyltin dioleate, dioctyltin dioleate, isooctyldimethyltin dithioglycolate, dibutyltin dineodecanoate, dimethyltin dineodecanoate, dioctyltin dineodecanoate, dibutyltin diacetate, dimethyltin diacetate, dioctyltin diacetate, dibutyltin bisacetylacetonate, dibutyltin bisdodecylthioalkylate, dimethyltin oxide, dibutyltin dilaurylthio, dimethyltin oxide, tin oxide, zinc, One or more of dioctyltin oxide, stannous octoate, dibutyltin maleate, dimethyltin maleate, dioctyltin maleate, monobutyltin oxide and stannous oxalate.

8. A method of preparing a plasticized polylactic acid composite according to claim 7, wherein: the addition amount of the organic tin catalyst is 0.1-1% of the molar amount of the lactide.

9. A method of producing a plasticized polylactic acid composite according to any one of claims 4, 5, 7 and 8, wherein: the molar ratio of the lactide to the polyol is 20-200: 1.

10. a method of preparing a plasticized polylactic acid composite according to claim 9, wherein: the heating reaction is carried out at the temperature of 130-160 ℃ for 4-6 h.